CSC105 Modern Database Design
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Questions and Answers

What does the entity-relationship (ER) data model help with?

  • Data storage
  • Data encryption
  • Data retrieval
  • Data modeling for use with databases (correct)

    • What are entities in the context of ER models?

    Tables that hold specific information.

    ER models cannot be represented by ER diagrams.

    False

    What is a weak entity?

    <p>An entity that cannot exist without a relationship with another entity.</p> Signup and view all the answers

    A department controls a number of ______.

    <p>projects</p> Signup and view all the answers

    Which of the following is a characteristic of independent entities?

    <p>Their primary key is not a foreign key.</p> Signup and view all the answers

    Name the two classifications of entities.

    <p>Independent entities and dependent entities.</p> Signup and view all the answers

    An independent entity is also called a weak entity.

    <p>False</p> Signup and view all the answers

    The Spouse table is a ______ entity.

    <p>weak</p> Signup and view all the answers

    What does the entity-relationship (ER) data model represent?

    <p>Both A and B</p> Signup and view all the answers

    ER diagrams cannot be translated to relational schemas.

    <p>False</p> Signup and view all the answers

    What is a weak entity?

    <p>An entity that cannot exist without a relationship with another entity and whose primary key is derived from the parent entity.</p> Signup and view all the answers

    An example of an independent entity in the COMPANY database is __________.

    <p>Employee</p> Signup and view all the answers

    Match the following characteristics with the type of entity:

    <p>Independent entity = Does not depend on another entity for existence Dependent entity = Exists based on the relationship with other entities Weak entity = Cannot exist without a relationship with a strong entity Strong entity = Can exist apart from all of its related entities</p> Signup and view all the answers

    What type of information does the COMPANY database contain?

    <p>Information about employees, departments, and projects.</p> Signup and view all the answers

    What identifies each associated table in dependent entities?

    <p>Foreign key</p> Signup and view all the answers

    Study Notes

    Database Design Phases

    • Consists of requirements collection, analysis, conceptual design, and relational database schema design.
    • Emphasizes the importance of understanding the "Miniworld" to tailor database design to specific needs.

    Entity-Relationship (ER) Data Model

    • Established for over 35 years, offering abstraction ideal for data modeling.
    • Easily translatable into relational models, resulting in ER schemas depicted through ER diagrams.
    • Based on two core concepts:
      • Entities: Tables storing specific information.
      • Relationships: Associations between entities.

    COMPANY Database Overview

    • Illustrates ER model concepts focusing on employees, departments, and projects.
    • Each department has a unique ID, name, office location, and a managing employee.
    • Departments oversee multiple projects that each have a unique name, number, and budget.
    • Employee records include name, ID number, address, salary, and birthdate, tied to a department, with project participation noted by start date and supervisors tracked.
    • Employee dependents are recorded, including their name, birthdate, and relationship to the employee.

    Entities Defined

    • Entity: An object in the real world identifiable from others, existing either physically (e.g., department, employee) or conceptually (e.g., project).

    Entity Weakness and Strength

    • Weak Entities: Existence-dependent on another entity, with primary keys derived from their parent. Example: Spouse table in the COMPANY database depends on Employee.
    • Strong Entities: Can exist independently, having primary keys that are not foreign keys. Examples include Employee and Department in the COMPANY database.

    Independent vs. Dependent Entities

    • Independent Entities (Kernels):

      • Serve as foundational elements in a database.
      • Possess a primary key that is not a foreign key and do not require association with other entities for existence.

    • Dependent Entities (Derived Entities):

      • Connect kernels together, existing dependent on one or more tables.
      • Often create associative tables with multiple foreign keys to establish many-to-many relationships.
      • Can contain additional attributes that enhance the linkage between associated tables.
      • Primary key options include composites of foreign keys or a combination with additional qualifiers if unique.

    Database Design Phases

    • Consists of requirements collection, analysis, conceptual design, and relational database schema design.
    • Emphasizes the importance of understanding the "Miniworld" to tailor database design to specific needs.

    Entity-Relationship (ER) Data Model

    • Established for over 35 years, offering abstraction ideal for data modeling.
    • Easily translatable into relational models, resulting in ER schemas depicted through ER diagrams.
    • Based on two core concepts:
      • Entities: Tables storing specific information.
      • Relationships: Associations between entities.

    COMPANY Database Overview

    • Illustrates ER model concepts focusing on employees, departments, and projects.
    • Each department has a unique ID, name, office location, and a managing employee.
    • Departments oversee multiple projects that each have a unique name, number, and budget.
    • Employee records include name, ID number, address, salary, and birthdate, tied to a department, with project participation noted by start date and supervisors tracked.
    • Employee dependents are recorded, including their name, birthdate, and relationship to the employee.

    Entities Defined

    • Entity: An object in the real world identifiable from others, existing either physically (e.g., department, employee) or conceptually (e.g., project).

    Entity Weakness and Strength

    • Weak Entities: Existence-dependent on another entity, with primary keys derived from their parent. Example: Spouse table in the COMPANY database depends on Employee.
    • Strong Entities: Can exist independently, having primary keys that are not foreign keys. Examples include Employee and Department in the COMPANY database.

    Independent vs. Dependent Entities

    • Independent Entities (Kernels):

      • Serve as foundational elements in a database.
      • Possess a primary key that is not a foreign key and do not require association with other entities for existence.

    • Dependent Entities (Derived Entities):

      • Connect kernels together, existing dependent on one or more tables.
      • Often create associative tables with multiple foreign keys to establish many-to-many relationships.
      • Can contain additional attributes that enhance the linkage between associated tables.
      • Primary key options include composites of foreign keys or a combination with additional qualifiers if unique.

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    Related Documents

    Unit 2.2 ER Model.pptx.pdf
    Unit 2.2 ER Model.pptx.pdf

    Description

    This quiz covers key concepts in modern database design, focusing on Entity-Relationship Modeling (ERM) and the various phases of database design. Test your understanding of relational databases and the analysis involved in building effective data models.

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